BRPI0722286A2 - SYSTEM AND METHOD FOR CONTROL OF A BRAKE SHOE - Google Patents

Description

"SYSTEM AND METHOD FOR CONTROL OF A BRAKE SHOE"

TECHNICAL FIELD OF THIS INVENTION

The present invention relates to a system and method for controlling and protecting a vehicle brake shoe device, particularly of trucks, buses and other heavy goods vehicles.

OVERVIEW OF THE INVENTION TECHNICAL STATE

A vehicle brake system usually comprises a brake shoe which is a basic drum brake or disc brake assembly with brake pads adjusted for each wheel axle or wheel that produces a braking force necessary to decelerate the vehicle. or bring the vehicle to a stop. If a brake shoe is overused, such as if it is applied several times over an extended period of time, fatigue or fading, that is, gradual or sudden loss of braking force, may occur. This is due to the fact that if brake pads are overused, their optimized working temperatures are exceeded and their coefficients of friction decrease as certain elements of a brake pad may begin to melt and / or to vaporize. Additionally, very frequent brake applications can cause large temperature variations in the brake and therefore cause thermal disc fatigue.

In order to protect a brake shoe, many vehicles are equipped with an additional auxiliary brake, such as a retarder. A retarder is a device that is permanently mounted to the engine or vehicle transmission to increase the braking capacity of the vehicle during prolonged brake application. Such an additional auxiliary brake may be used to protect a brake shoe and to give the driver greater control and improved brake performance.

Modern vehicles are also often equipped with an adaptive or intelligent cruise control system that can automatically adjust vehicle speed to maintain a safe tracking distance for a moving vehicle ahead or to keep the vehicle at a preset speed. An ACC 10 device usually uses a radar mounted behind the vehicle grille to detect the speed and distance of the vehicle ahead. If the vehicle ahead reduces (slows down) or moves slowly or the preset speed is exceeded, the ACC device sends a signal to the vehicle's engine or braking system to decelerate. After that, when the road is clear, the ACC device speeds the vehicle back to a preset speed. As a result, the ACC device controls the braking behavior of the vehicle.

U.S. Patent No. 6,044,321 describes

Such an adaptive cruise control system for a vehicle, wherein applying a brake is defined by maintaining a defined vehicle-to-vehicle distance. In the event that adaptive cruise control decides that a braking operation is required to maintain the defined vehicle-to-vehicle distance, a retarder is applied and if retarder application is not sufficient, an automatic brake is continuously operated until the vehicle-to-vehicle distance will be conquered.

Unfortunately, the braking behavior applied

The state-of-the-art adaptive cruise control system is not applicable for loaded heavy vehicles such as trucks as continuous operation of the brakes, particularly the brake shoes, easily results in overuse of the system. of vehicle braking. But also, brakes of all other vehicle species show increased fatigue due to the continuous activation of 5-brake shoes by an adaptive cruise control system in order to maintain distance to a vehicle ahead when driving behind the wheel. a slow vehicle, for example on a steep slope.

Accordingly, it has been suggested in International Patent Application No. WO 2007/078230 to disengage the ACC device in the event that the brake temperature exceeds a preset threshold. But that also means that the driver needs to be informed that the ACC device is disabled and that driver must take control immediately, which reduces driving comfort and is not desired by the driver.

SUMMARY OF THIS INVENTION

It is therefore an object of the present invention to provide an automated system and method for controlling and protecting a brake shoe in a vehicle, which reduces the risk of harmful brake shoe thermal fatigue problems.

This is an object solved by a system and method for controlling and protecting a brake shoe of a vehicle in accordance with independent patent claim 1 and independent patent claim 15, respectively, subsequently; and as well as by a cruise control device comprising such a system in accordance with independent patent claim 20 later, or performance of such a method also in accordance with independent patent claim 20 later.

The present invention is based on the general idea that a brake shoe is best protected if frequent or long-term applications of a brake shoe are minimized. Accordingly, the system comprises a control unit that limits the usability of the brake shoe 5 to a predetermined total application time of the brake shoe within a predetermined time interval.

The total brake shoe application time can be added from several short brake shoe application times 10 over the predetermined time interval. This means that, for example, if the total application time of the brake shoe is predetermined to 12 seconds within a 60 second time interval, the brake shoe may be applied 3 times for 4 seconds 15 during the interval. 60 second time. This ensures that the brake shoe is not overused and fatigue and damage due to excessive use of the brake shoe is minimized.

Application of the brake shoes is preferably initiated if / when the vehicle reaches a minimum distance for a vehicle moving ahead or exceeds a maximum speed. The minimum distance and maximum speed can advantageously be detected by an adaptive cruise control device, where the minimum distance 25 is defined as the distance the vehicle at least needs to avoid colliding with a vehicle ahead if the vehicle to forward suddenly stops or slows down significantly. Top speed is the highest speed the vehicle can safely travel on the road. Both the minimum distance and maximum speed are dependent on environmental conditions such as road slope, road conditions, weather conditions and / or characteristic vehicle conditions such as vehicle speed, vehicle weight, load capacity, braking force and / or intervehicle conditions (between vehicles), such as intervehicle velocity (between vehicles).

On the other hand, the time between applications of the 5 brake shoes is not determined. Consequently, the brake shoe may be applied, for example, for 3 seconds, released for 15 seconds, re-applied for 5 seconds, released for 12 seconds, re-applied for 2 seconds, released for 20 seconds, and then re-applied. applied for 10 2 seconds, yet easily fulfills the condition of the maximum total application time of 12 seconds within the predetermined time interval of 60 seconds.

In a further preferred embodiment of the present invention, the release time interval depends on whether the vehicle reaches the minimum distance to the vehicle ahead or exceeds the maximum speed again. This means that, for example, if the vehicle is driving down a sloping road, the brake shoes are applied for a few seconds until the distance to the vehicle ahead 20 becomes significantly greater and then the brake shoes are released and the vehicle is able to "roll" to the minimum distance and / or the maximum speed again.

Preferably, during the application of the brake shoes, the required braking force and, consequently, the application time and the resistance of the brake shoe are calculated to enable the vehicle to rotate for a plurality of seconds without Re-apply the brake shoes before the minimum distance and / or a maximum speed is reached. This calculation of the required braking force also takes into account environmental conditions such as road inclination, road conditions, weather conditions and / or characteristic vehicle conditions such as vehicle speed, vehicle weight, load capacity. , braking force and / or intervehicle conditions, such as intervehicle velocity.

The total application time of the brake shoes and the predetermined time interval are preferably preset by a vehicle manufacturer or brake manufacturer and can be optimized for vehicle and permissible vehicle load capacity.

In another preferred embodiment of the present invention, the maximum total application time and time interval are predetermined each time the vehicle starts to drive or is activated. But, it is also possible that the driver himself can start determining the total application time and time interval. This has the advantage that the total application time can be adapted to the current (current) vehicle condition, for example by driving with or without load, whereby the brake shoes can be additionally protected.

In a further preferred embodiment of the present

invention, the vehicle additionally comprises at least one auxiliary brake device which may be applied throughout the deceleration process.

Additionally, the vehicle preferably comprises an adaptive cruise control device having a distance sensing unit for detecting a distance for a vehicle ahead and / or a speed limitation unit for limiting the maximum speed of a vehicle. In the event that a predetermined distance 30 to the vehicle ahead is detected or where the vehicle exceeds the maximum speed, the auxiliary brakes and / or brake shoes are applied to slow down. the vehicle.

In the event that the vehicle ahead is too slow or the vehicle is traveling down a sloping road, the braking force applied by the auxiliary brakes may not be sufficient for the required deceleration. Then the system can additionally apply the brake shoes to provide sufficient braking force.

Additionally, a cruise control device comprising a preferred embodiment of the system of the present invention or being adapted to perform an embodiment of the method of the present invention is preferred.

BRIEF DESCRIPTION OF THE DRAWINGS OF THE INVENTION

In the following, the present invention will now be described in greater detail with reference to the accompanying Figure Drawings. The illustrated embodiments of the Drawings of the Figures are exemplary only and are not intended to restrict the scope of the present invention to them. The scope of the present invention is further defined by the patent claims.

The Drawings of the Figures show:

Figure 1 is a schematic top view of a vehicle comprising a system in accordance with an embodiment of the present invention;

Figure 2: is an illustration of a descent following scenario;

Figures 3A - 3C: is an additional illustration of the descent following scenario;

Figures 4A - 4C: is a schematic comparison comparing a standard braking strategy and an embodiment of the braking strategy of the present invention;

Figure 5 is a diagram of the braking duration factor (BD) as a function of time (t); Figure 6 is a simulation of a different vehicle parameter behavior when using a preferred embodiment of the method of the present invention;

Figure 7: is a diagram of an acceleration as a

vehicle weight and descent slope function; and

Figure 8 is a Yog file of a test performed with a truck comprising a preferred embodiment of the truck system.

present invention.

The Figures are only schematic representations and the present invention is not limited to the embodiments depicted therein.

DETAILED DESCRIPTION OF THIS INVENTION

Figure 1 shows a vehicle (10) comprising a system (12) for controlling the brake shoes (14) of the vehicle (10). A disc or drum brake assembly constituting a brake shoe (14) is mounted (fixed) on each end of each vehicle wheel axle (10). When the vehicle driver (10) depresses the foot brake pedal (18), the brake shoe (14) produces the braking force 25 necessary to bring the vehicle to a stop via the wheels (16). The system (12) comprises an ACC device (20) which detects the speed and distance of any road users ahead of the vehicle (10) and automatically adjusts the vehicle speed to maintain a safe tracking distance. The ACC device 20 utilizes one or more auxiliary brake devices and the vehicle brake shoe to maintain the desired speed and to maintain the desired distance for a vehicle ahead of the vehicle. The system (12) distributes the desired braking force by the ACC device to the auxiliary brake devices and to the brake shoe or disc brake assemblies (14). This combination of braking force for the auxiliary brake devices 5 and the brake shoe is well known to the person skilled in the art and is not described in detail. The vehicle may be a single vehicle or a vehicle combination, for example a tractor / trailer combination. The vehicle is preferably a heavy vehicle 10, such as a truck, bus or construction vehicle.

Figures 2 and 3A through 3C illustrate a downward tracking scenario with inefficient brake assist braking capability, which is the typical application for the present invention.

Figure 2 shows a vehicle (10) (ego vehicle) that is exactly around following a vehicle (24) (target vehicle) descending a long downhill (long downhill stretch), wherein the ego vehicle (10) is heavier than the target vehicle (24), for example, due to the load capacity, which results in a higher downward tilt force. The vehicle (10) is equipped with an ACC device (20) comprising a preferred embodiment of the system of the present invention (12) and a radar mounted behind the vehicle grid (10) for detecting the speed and distance of the other vehicle ( 24). The ACC device (20) is arranged to keep the vehicle (10) moving at a preset speed when no vehicle is ahead of the vehicle (10), and to keep the vehicle (10) at a desired distance (d ) behind a vehicle when there is a vehicle in front of the vehicle (10). To the extent that vehicle (10) is heavier than vehicle (24), the required brake force is higher for vehicle (10) than for vehicle (24). Consequently, the braking forces of the auxiliary brakes are not sufficient to maintain a constant distance to the vehicle ahead.

As soon as the vehicle (10) gets too close to the target vehicle (24), the ACC device (20) sends a signal to the system (12) to slow down the vehicle (10) which in turn applies the brake shoes. (14) vehicle (10) so as to maintain the desired distance (d) between vehicles (10) and (24). The brake shoes (14) are applied to the extent that the auxiliary brake alone cannot maintain the desired distance (d). The distance between vehicles 10 and 24 may be defined as a time gap in seconds or as a distance in meters.

Troublesome braking and distance maintenance are illustrated in Figures 3A through 3C. As shown in Figure 3A, the ego vehicle (10) having at least one auxiliary brake device and at least one brake shoe approaches the vehicle ahead (24) (= target vehicle), whereby the ego vehicle ( 10) has a higher speed than the target vehicle (24) (Vego> Valvo). In addition, it is assumed that the ego vehicle 10 and the target vehicle 24 are moving downhill having an acceleration (aego) and a (target) due to the inclination of the road, whereby an auxiliary brake capability Insufficient adds to the acceleration (a & go) of the ego vehicle (10).

At a given distance (dl), derived from the intervehicle velocity (vrel) and a critical minimum distance (critical) that does not have to be under-run [(critical) defines the absolute minimum distance that the vehicle ego must be maintained so as not to collide with the vehicle ahead] and / or the driver selects, brake shoes are applied with deceleration: & brake £ (& ega — tilt (dl)) + £ (Vre ^ fd) í

where [a.ego ^ incunation (dl) J is the acceleration of vehicle ego (10) before distance (dl), (vrel) is the relative velocity of the intervehicle: [vrei = Vaivo ~ Vegolr and (d) is the distance between the ego vehicle (10) and the target vehicle (24).

The distance (dl) is not constant, but it is a function of (Vrel), as in this case the ego vehicle (10) is much faster than the target vehicle (24), a more early reaction is needed as for a leisurely ego vehicle (10).

The time required for the ego vehicle 10 to decelerate to the same speed as the target vehicle 24 is (t12). During this time, the distance between the target vehicle 24 and the ego vehicle 10 must further be decreased to (d2), see Figure 3B. It is therefore necessary for the distance determination (dl) to take into account that the ego vehicle (10) is still approaching the target vehicle (24) for a time (t 12). The distance (d2) should be equal to or greater for an absolute minimum (critical) distance, the ego vehicle should maintain for the target vehicle (24).

As shown in Figure 3C, the deceleration is maintained at (cipher) until the distance between the ego vehicle (10) and the target vehicle (24) becomes (d3). There the brakes are released and the ego vehicle (10) coarsely accelerates (ego-induction), assuming that ambient conditions do not change much. The distance that ego vehicle 10 can roll until it reaches a (minimum) distance to target vehicle 24 where the brakes need to be applied again is (d3).

distance fdm / n, n, J is only identical to (dl), if roughly the same relative velocity (vrel) is determined. In the event that the target vehicle 24 accelerates or decelerates or the ambient conditions change, it differs from (dl).

The accelerations (aego) of the ego vehicle (10) are

directly coupled to how brake shoes and auxiliary brakes should be applied to prevent brake shoe fatigue. In the system of the present invention, fatigue is defined as a function of time of applying brake shoes. To avoid fatigue, the system adds brake shoe application times and limits brake shoe usability to a predetermined application time over a predetermined time interval.

It was discovered by the inventors by empirical testing.

Fatigue can be very well avoided if the predetermined total application time is in the range of 10 seconds to 20 seconds over a predetermined time interval in the range of 40 seconds to 60 seconds. At follow-up, the predetermined total application time is set to 15 seconds and the time interval is predetermined to 50 seconds.

The approach to indirectly controlling brake shoe fatigue by intermittently applying brake shoes for a short time also means that the distance (d) should be made possible to decrease to the minimum distance before the brake shoes

brake may be applied. In other words, the ego vehicle (10) does not maintain a predetermined distance (dajugte) to the target vehicle (24) as described in the prior art, but the distance (d) is possible to vary around a given range. distance (dajUBte) ·

The variation around the determined distance (dajuete) is created by controlling the braking force of vehicles following, that is, by switching between use of auxiliary brakes and auxiliary brakes and / or brake shoes. In situations where the auxiliary brakes are saturated due to the downhill pull, the brake shoes are briefly applied (preferably within the range of 3 seconds to 5 seconds) to increase the current distance (d) for a vehicle ahead. .

Brake shoes are applied at the last moment when the current distance (d) is equal to a critical minimum distance fd ™. The minimum distance () is the shortest possible distance between the ego vehicle (10) and the target vehicle (24) and this distance varies with the relative intervehicle velocity (vrel), the severity of road inclination, loading condition, and auxiliary brake performance. The different distance values fulfill the following relationship:

(minimum) - (d) ^ (dajUS £ g).

Figure 4 shows the braking strategy of the present invention compared to the state-of-the-art braking strategy, where the state of the art is shown in Figure 4A and the strategy of the present invention is illustrated in Figure 4B.

Figure 4A shows the target vehicle (24) and the ego vehicle (10). At a certain distance (dajU8te), adjusted by the driver or the ACC1 system, the ego vehicle (10) applies the brake shoes in addition to the auxiliary brakes (FB + AB) to reduce the distance (d) to the target vehicle. at the front (24). As the distance to the vehicle ahead and the distance to a braking alert point (26) is rather long, the brake shoes are only slightly applied resulting in a relatively small braking force and a relatively increased small in distance. Consequently, after a short period of time, the ego vehicle (10) has reached the distance (dajUste) and the brake shoes have been re-applied, which may result in overuse of the brake shoes causing fatigue.

The distance (adjustment) can be adjusted by the driver through a human machine interface (HMI), particularly a switch, button or menu. It is also possible that the system has been storing a preset value (even setting) or even that the system has been monitoring the driver's behavior and suggesting values (setting) depending on traction situations and correspondingly adjusted (setting) values already experienced. / os.

To the extent that, in accordance with the present invention, the use of brake shoes is limited to a predetermined total application time over a predetermined time interval, it is advantageously also to use a new and inventive braking strategy. Instead of applying the brake shoes at a given distance (adjustment), the ego vehicle (10) is allowed to roll to the target vehicle (24) to a minimum distance (d ', - ,, ·',). Not until the minimum distance (djiunima) to the target vehicle (24) is reached, the brake shoes are applied with reasonable braking force for several seconds (preferably from 3 seconds to 5 seconds), whereby the The distance to (d) from the target vehicle (24) is significantly increased. At a return point (lap) (28), well before the braking alert point (26), acceleration returns (lap) to a deceleration so that the distance to the vehicle ahead begins to increase. Preferably, the increase in distance (d) is so large that the brake shoes do not need to be applied for a rather long time (for example more than 10 seconds) and therefore have a cooling capacity. Thereby, thermal fatigue is reduced and the service life of the brake shoes is increased.

For calculating the required distances, application times and release times, the system of the present invention preferably utilizes a parameter called braking duration factor (BD). It is understood by one of ordinary skill in the art that the following description relates to a preferred embodiment. Any other possible approach to determining distances, application times, release times, braking force, etc. are also included within the scope of this patent application.

The braking duration factor (BD) that monitors the application times of the brake shoes used in this preferred embodiment is defined by:

f2

BD (t) = jdt + BD (t 1)

f1

(1)

if brake shoes are applied; and t2

BD (t) = -jadt + BD (U)

<1

(2)

if brake shoes are not applied;

where (a) is a constant.

The constant (a) is determined by dividing the predetermined total application time with the predetermined time interval. As explained earlier, the inventors have found that brake shoes can be better protected by adjusting the predetermined time to 15 seconds and the time interval to 50 seconds.

seconds, which results in a = -.

50

The braking duration factor (BD) may also depend on one or more of the following parameters: vehicle speed, brake pressure, brake disc temperature, ambient temperature, brake disc type, brake pad type. It is also possible to have different braking duration factors depending on these parameters. The constant (a) may also vary depending on these and other parameters. The braking duration factor (BD) can be calculated over a fixed time interval, ie the braking duration factor (BD) calculation is done over a fixed time interval and thereafter set to zero before the next calculation is done. The braking duration factor (BD) can also be calculated over a fluctuating time interval, ie the braking duration factor (BD) calculation is done continuously.

Figure 5 shows a diagram illustrating the development and summarization of the braking duration factor (BD) over (over) time (t). The brake shoes of the vehicle have not been used for a long time, therefore the braking duration factor (BD) is zero in time (t) = 0. 0 predetermined total application time (32) and, therefore, the maximum braking duration factor (BD) limit is set to 15 seconds within a time interval (30) of 50 seconds in this example. When the brake duration factor (BD) reaches this limit, the use of brake shoes is limited. The application time of the brake shoe is indicated by the reference signal (34), where the release time of the brake shoe is indicated by the reference signal (36).

As can be seen in Figure 5, at time (t) = 5, the vehicle brakes for 5 seconds. Adjusted for the above equations, this results in a braking duration factor (BD) of 5 in time (t) = 10 by using equation (1) as the vehicle is braking:

10

15

10

SD (f = 10) = jdt + BD (t = 5) = 5 + 0 = 5

After that, the brakes are not engaged for 3 seconds. This results in a braking duration factor (BD) of 4.1; using equation (2) as the vehicle is not braking. The constant (a) is here 15/50.

BD (t = 13) = -J- df + BD (t = 10) = -— * 3 + 5 = 4.1 ■ iq 50 50

At (t) = 13, the brakes are re-applied for 10 seconds, resulting in a braking duration factor (BD) of 14.1 by using expression (1).

23

BD (t = 23) = J df + BD (f = 13) = 10 +4.1 = 14.1

13

At (t) = 23, the brakes are released for 7 seconds and then re-applied for 2 seconds, which again results in a braking duration factor (BD) of 14. 3J? 1 c

BD (t = 30) = - \ ±? -Dt + BD (t = 23) = -— * 7 + 14.1 = 12 23 50 50

32

SD (t = 32) = J df + BD (f = 30) = 2 + 12 = 14

30

This means that the maximum braking time factor (BD) limit is approximately reached and the next release time should be long enough to have sufficient time for the brake shoes to cool. This in turn means that the distance to the vehicle ahead or the vehicle deceleration achieved after the last braking must be large so that the brake shoes can again be released long enough to allow them to cool down. .

Therefore, the distance (d) that must be achieved by activating brake shoes to enable the brake shoes to cool and fulfill the condition of full application time setting over a predetermined time interval having to carefully calculated and, in this embodiment, is based on an estimated addition of a cycle (brake shoes are applied, released and re-applied) to the braking duration factor BD (t), symbolized (ABDgestimated) / which is defined by:

15

ABDgstimado - t - TroIagam

An "advanced simulation" has to (in this case, an analytical solution), therefore, be made on each sample to calculate an estimate of the "rolling time" (Trojan), that is, the time should take the vehicle to follow. reach (minimum) once the brake shoes are released. The rollover time, or brake shoe remaining time, is calculated by the following equations (estimate is performed during a brake shoe activation 5), in which it is further assumed that the vehicle speed ahead (ValvoJ is constant and that The braking force from the auxiliary brakes and the resistive forces, such as, for example, road slope, air, roll, etc., are all constant:

10

Vegoaa (t) - Vego (tFBapl) + 3ego (tFBapl) * t, which:

(t) s [application start FB = tFBapl, application end FB = trareI];

15

dest (t) is the estimated distance if the brake shoes are released in time (t);

Vesoest (t) is the estimated ego vehicle speed if the brake shoes are released in time (t);

20

d (tFBapl), indicates the time distance t = tFbapi;

Yaivo (tFBapi) * indicates the target vehicle speed in time t = tFbapl;

aeffo (tFBaPi) r indicates the acceleration of target vehicle at

time t = tFbapl ΐ

25

Yego (tFBapi) r indicates the vehicle speed following in time t = tFbapi;

where t = tFBapi is when (minimum) is reached and the brake shoes must be used.

By choosing which dest (t) = d (tFBapi), and assuming

stationary conditions (constant target vehicle speed, constant road slope, constant resistance forces), the rolling time, (Rollover) r can be calculated:

T-X-JUit- (Ve90 (* FBapl) ~ Valvo (tFBapl) - T (tFBapl) * aego (tFBapl))

aego (tFBapp)

Vego (tFBapl) - Valvo (tFBapl) - T (tFBapl) * aego (tFBapl) ^ o (d (tFBapl) --- T (tFBax) * Vego (tFBapl) ^ ego (tFBapl) --- ---- ---: - ^ 3ego (tFBapl) 5

This means that the increment for the braking duration factor (BD), ie (ABDest), can be calculated.

To the extent that BD (t) and increment (ABDest) depend on

of a plurality of variables, the braking duration factor (BD) can be indirectly controlled by any suitable value. In most situations, the strategy for applying the brake shoes until the 15 increment (ABDest) has reached zero and then releasing the brake shoes and enabling a roll with saturated auxiliary brakes can be performed smoothly as which also means that the braking duration factor (BD) will never exceed the preset allowed value of 15 seconds.

Figure 6 shows a simulation of the previously explained method, in which it is assumed that a truck having a total weight of 40 tons is traveling down a 6% incline with a speed of 20 m / s. As can be seen from Figure 7, the total utilization of the vehicle's engine brakes (= auxiliary brakes) will create an acceleration of 0.25 m / s2.

Figure 7 shows the acceleration (aego) of the ego vehicle (10) as a function of weight (m) and descent slope (a), where truck weights (m) are typically in the range of from 20 tons to 60 tons. The vehicle engine brake (VEB) (= auxiliary brake) is fully engaged and the travel position is selected to determine an engine speed of approximately (discrete gearbox) 1800 rpm. The ego vehicle speed (10) is assumed to be 20 m / s. As can be seen, in extreme situations [60 tonnes and 16% of road inclination (a)] the acceleration (aego) of the ego vehicle (10) due to the downhill inclination force is 1.2 m / s2. For more realistic situations [40 tonnes and slope (a) <8%] the acceleration is always <0.5 m / s2. Measurements on a road having a slope of (a) = 6% determined a maximum acceleration of 0.25 m / s2 for a vehicle of 40 tonnes.

Consequently, the critical (assumed) critical acceleration for the simulation shown in Figure 6 is adjusted to 0.25 m / s2. It is further assumed that a comfortable brake shoe activation will change the acceleration from 0.25 m / s2 to -1 m / s2 (ie the deceleration is

4 times higher than acceleration), and a target vehicle speed is constant, [(Valvo) = constant]. Brake shoes are intended to be fully recovered after they have been applied, which corresponds to a low braking duration factor (BD) [i.e. (BD) = 0] when in time to re-apply the brake shoes. brake to increase the distance to the vehicle ahead.

In Figure 6, the various vehicle parameters are shown as a function of brake shoe application time. The first diagram of Fig. 6 - Fig. 6A shows the velocity of the ego (vego) vehicle ranging from 18 m / s to 22 m / s, where (Valvo) is constant at 20 m / s.

The second diagram of Figure 6B shows the development of the time gap values (38) - in other words the distance - relative to the brake shoe application time (34) and release time (36). The top curve in Figure 6B shows the development of time gap values (38) which are increased from 1.2 seconds to approximately 2 seconds to ensure that the brake shoes are not overused. The lower (lower) curves show the corresponding application of the brake shoes that are applied for 4.7 seconds (34) and released for 18.5 seconds (36). This ensures that the braking duration factor (BD) is zero after each cycle [see for (BD) Figure 6C]. It can also be seen from Figure 6B that the brake shoes are applied slightly harder at the beginning of the brake intervention (1.2 m / s2) to comfortably reduce relative speed [see reference signal (40)] .

The last diagram of Figure 6, Figure 6C, illustrates the behavior of the braking duration factor (BD) as calculated after the previously determined equations. As can be seen, the braking duration factor (BD) reaches zero, which means that it is fully recovered when in time to re-apply the brake shoes in order to increase the distance to the vehicle ahead.

The simulation behavior is similar in reality as can be seen by comparing Figure

6 and Figure 8, in which Figure 8 shows a Yog file from a downhill slope test of Kalleback, Sweden, where a truck was used driving 10 km / h faster than a target vehicle . The standard ACC function of the truck has been deactivated and replaced with a preferred embodiment of the system of the present invention.

The longer the distance between the truck and the target is greater than (cL, ^^) the truck was able to accelerate by requesting a defined engine torque (using a simple throttle controller) to simulate the effects of a Truck loaded on a slope.

If the distance is less than (d ^, ·) the brake shoes are applied in accordance with the braking strategy of the present invention as illustrated in Fignra 4B. The sooner the brakes are activated, a calculation is running to check when the distance to the target vehicle is increased excessively, than the expected time (trolley) to accelerate again with the same acceleration before the brakes are activated compared to the activation time. brake current does not increase the braking duration factor (BD) 1 which means that the braking duration factor (BD) has been returned to zero before the brake shoes are reapplied. This is usually determined if the expected brake release time is 50/15 times higher than the current brake activation time. Braking duration factor (BD) behavior is illustrated in graph (42) of Figure 8.

As shown in Figure 8 the truck accelerates by 0.4 m / s2 until the distance to the target vehicle has decreased to (dm; (here about 1.3 seconds) as the truck is driving 10 km / s). h faster than the target vehicle The distance measurement for the target vehicle is illustrated in graph (44), where the corresponding time gap is shown in graph (46).

If the distance Cdminima; has been achieved, the brakes are applied at approximately -1.5 m / s2 for about 4 seconds. Under that time the speed of the trucks is reduced and the distance increases. The graph (48) of Figure 8 shows the truck speed behavior that is significantly reduced by applying the brake shoes - see reference signal (47) - and then the truck is allowed to re-accelerate to the previous speed - see the reference signal (49). The corresponding application of the brake shoes is indicated by the graph (50) with application times indicated by (34) and release times indicated by (36).

The brakes are released when the calculated acceleration time with the same acceleration before braking is sufficient to enable the braking duration factor (BD) (increased by 1 second) to return to zero and decrease to -15 / 50 while the brakes are not applied. Thus, the result for the braking duration factor (BD) after a braking / non braking cycle is approximately zero.

To achieve the required brake release time, the required deceleration rate is rather high (about 4 times the positive acceleration due to the inclination), which is about -1.2 m / s2 to -1.6. m / s2 or even more, depending on the relative speed, but is in this example limited anyway to the overall ACC limit of -2 m / s2. Braking is adapted to start smoothly so that despite high levels, braking is experienced as comfortable. Brake activation time of about 3 seconds - 4 seconds and brake level are determined to reflect the behavior of a normal truck driver in a downhill traction situation.

The difference between traction on a flat road and a downhill road can be observed by comparing the variation in the graphs before and after 130 seconds, which is indicated by the vertical line (52).

Before 130 seconds on the timeline, both vehicles were running on a plane and after that both vehicles are pulling down the slope at Kalleback. Here, the braking duration factor (BD) does not fully return to zero after one cycle, but is increased by approximately a factor of 1.4 after each cycle. This is due to the acceleration limit overtaking directly after release of the brakes while accelerating downhill, as the calculation only considers acceleration measured directly before braking, which is correct for homogeneous acceleration caused by a fully loaded vehicle. on a slope.

The present invention should not be construed as being limited to the exemplary embodiments described above, and it will be appreciated by those skilled in the art that a number of variations and modifications are conceivable within the scope of protection and inventive concept of the present invention as established by the patent claims later.

Claims (20)

1. A system for controlling a brake shoe of a vehicle having at least one brake shoe device, characterized in that the system comprises a control unit that limits brake shoe usability for a full application time. brake shoe within a predetermined time interval and the control unit further adjusts a brake shoe braking force such that a deceleration provided during the brake shoe application time enables the vehicle turn without re-applying the brake shoe for a predetermined brake shoe remaining time. The system according to claim 1, characterized in that the system additionally comprises a unit of calculation which calculates a braking duration factor (BD) for addition of application time periods and release time periods. brake shoe within the predetermined time interval for the total application time of the brake shoe. The system according to claim 2, characterized in that the calculation unit additionally calculates an increment (ABD) for the braking duration factor (BD) which determines the remaining brake shoe time, where the increment (ABD) is preferably added for the braking duration factor (BD). The system according to any one of the preceding claims, characterized in that the system further comprises a distance detection and calculation unit for detecting a distance for a vehicle ahead and calculating a minimum distance for a vehicle at a distance. and / or a speed limitation unit for adjusting a maximum speed limit for the vehicle, and where the control unit applies the brake shoe if / when a predetermined minimum distance for a vehicle ahead is detected. and / or the maximum setting speed is exceeded. The system according to claim 4, characterized in that the minimum distance and / or maximum speed are / are determined depending on ambient conditions, particularly road inclination, road conditions and / or weather conditions. The system according to claim 4 or 5, characterized in that the minimum distance and / or maximum speed are / are determined depending on a characteristic vehicle condition, particularly vehicle speed, vehicle weight and / or auxiliary brake performance. The system according to any one of claims 4 to 6, characterized in that the determined minimum distance and / or maximum speed are / are constantly re-determined by the calculation unit. The system according to any one of claims 4 to 7, characterized in that the control unit further adjusts the brake shoe braking force in accordance with the minimum detected distance, the detected speed limit, and / or the braking performance of the auxiliary brake. The system according to claim 8, characterized in that the control unit adjusts the braking force taking into account ambient conditions, particularly road inclination, road conditions, weather conditions. The system according to claim 8 or 9, characterized in that the control unit adjusts the braking force taking into account vehicle characteristic conditions, particularly vehicle speed, vehicle weight, load capacity, and / or intervehicle conditions, particularly intervehicle velocity. The system according to any preceding claim, characterized in that the system additionally comprises a storage unit, in which the total application time of the brake shoe and the time interval predetermined by a vehicle manufacturer or Brake manufacturers are stored. The system according to any one of claims 1 to 11, characterized in that the calculation unit is further adapted to predetermine the total application time of the brake shoe and the time interval, preferably each time. the vehicle starts to drive or is activated. The system according to claim 12, characterized in that the system additionally comprises a human / machine interface which enables a vehicle driver to start predetermining the total application time of the brake shoe and the time interval. The system according to any preceding claim, characterized in that the predetermined total application time of the brake shoe is in a range between 10 seconds and 20 seconds and the predetermined time interval is in a range. between 45 seconds and 65 seconds. 15. A method for controlling a brake shoe of a vehicle having at least one brake shoe device, characterized in that the method comprises the steps of: • limiting brake shoe usability for a full application time predetermined brake shoe within a predetermined time interval; and • adjusting a brake shoe braking force such that a deceleration provided during the brake shoe application time enables the vehicle to run without re-application of the brake shoe for a remaining brake shoe time. predetermined. The method according to claim 15, characterized in that it further comprises the step of calculating a braking duration factor (BD) for adding the application time periods and the release shoe time periods. brake within the predetermined time interval for the total application time of the brake shoe. The method according to claim 16, characterized in that it further comprises the step of calculating an increment (ABD) for the braking duration factor (BD) which determines the brake shoe remaining time, wherein the increment (ABD) is preferably added for the braking duration factor (BD). The method according to claims 16 or 17, characterized in that: • The braking duration factor (BD) is calculated in accordance with: <formula> formula see original document page 30 </formula> for application â brake shoe; and <formula> formula see original document page 31 </formula> for brake shoe release, and / or • The increment (ABD) for braking duration factor (BD) is calculated in accordance with: Abd = t - a * Tup_roll with Tup_rojj indicating the brake shoe time remaining; and wherein (a) is a constant, determined by dividing the predetermined total application time with the predetermined time interval. The method according to any one of the preceding claims, characterized in that the method is performed on a system as defined in any one of claims 1 to 14. Cruise control device, characterized in that it comprises a system for controlling a brake shoe of a vehicle as defined in any one of claims 1 to 14, wherein the cruise control performs a method as defined in any one. one of claims 15 to 19.